1. Field of Invention
The present invention relates to bowling ball accessories, and more particularly to a device adapted for use in marking and orienting bowling balls to provide coordinate markings thereon for use in accurately determining the proper location and disposition of the finger and thumb holes with respect to the pin and/or center of gravity and/or mass bias of a bowling ball.
2. Discussion of Prior Art
As the design and construction of the bowling ball continues to develop and evolve, it has become increasingly important to ensure the proper orientation of the finger and thumb holes in relation to one or more of the three physical properties of the modern bowling ball. These properties are:
Center of gravity; this is a radial projection on the surface of the ball of the physical center of gravity of the bowling ball before drilling the gripping holes. Placement of this helps determine the final static weights of the ball. These static weights, and thus the placement of the center of gravity, determine in part how the delivered bowling ball will react with the surface of the bowling lane.
Reference Pin; this indicates the center of the weight block along its longest axis. Once under rotational motion, as in the case of a rolling bowling ball, the weight block generates inertial forces which cause the rotational axis to migrate until the weight block is either in direct alignment with the rotational axis or orthogonal to the rotational axis. By aligning the reference pin and weight block in relation to the rotational axis initiated by the bowler, the drilling technician may determine how far the rotational axis will migrate. The effect of the rotational axis migration is seen on the surface of the bowling ball as spaced rings of lane conditioner picked up during the travel of the ball down the lane and is commonly referred to as the track flare of the ball. The greater the axis migration, the greater the spacing of the oil rings. Greater oil ring spacing ensures that clean ball surface is presented to the lane surface and increases the amount of friction the ball is able to generate with the lane surface. Once again, this will determine in part how the bowling ball reacts with the lane surface.
Mass bias or preferred spin axis; this is an indication on the ball surface of one end of the axis about which the ball would experience equilibrium while under rotational motion. Rotation about any other axis will cause the rotational axis to migrate toward the preferred spin axis or mass bias location, thus producing the track flare which bowlers see on their ball. This too helps determine how much and where on the lane the ball will hook.
In practice, one or more of these three ball properties are placed at a desired distance(s) from the axis the ball rotates about as it leaves the bowler's hand during delivery. The location on the surface of the ball at the end of this axis which would be visible to the bowler during delivery is know as the positive axis point. The positive axis point for a given bowler is not influenced by the balance or layout of the ball, and can therefore be easily acquired from any ball the bowler currently uses. Once the bowler's positive axis point is located on the ball surface prior art tools such as are disclosed in U.S. Pat. No. 3,161,041 to Amburgey (1964), or U.S. Pat. No. 5,603,165 to Bernhardt and Laskow (1997) are used to measure the distance left or right of the center of the bowler's grip and the distance up or down from that line. The left/right measurement is normally referred to as the horizontal coordinate of the bowler's axis point. The measurement up/down is referred to as the vertical axis coordinate of the bowler's axis point. The device disclosed in U.S. Pat. No. 5,813,129 to Tseng could also be used to obtain these measurements, however this device is not commercially available at this time.
Using any of the prior art tools for this task starts by drawing a grip center line which bisects the thumb hole and extends through the center of the bridge between the finger holes. The tool must then be repositioned to measure and mark the midpoint of the grip center line between the gripping face of the thumb hole and the gripping faces of the finger holes. The tool must then be repositioned again and a second line drawn perpendicular to the grip center line from the midpoint of the grip center line and generally toward the bowler's positive axis point. The tool must then be repositioned again to draw a third line orthogonal to the second line and passing through the marked positive axis point. The tool must then be used to measure the length of the second line segment which connects the midpoint of the grip and the third drawn line; this is the horizontal axis coordinate and this line defines the horizontal axis plane. The length of third line segment connecting the second line to the positive axis point must then be measured to provide the vertical axis coordinate; this line defines the vertical axis plane. Using prior art tools to obtain these measurements is a very time consuming process.
In preparation to drill the new ball, it is common practice for the drilling technician to first determine the desired location of the bowler's positive axis point relative to one or more of the ball's marked properties (reference pin, center of gravity, or mass bias.) For instance, it may be that to achieve the desired reaction the reference pin should be 4 inches from the positive axis point and the center of gravity should be 5 inches from the positive axis point. To achieve this result using prior art tools the drilling technician must measure the desired radius from the desired ball property indicator (reference pin, center of gravity, or mass bias); pencil a small mark on the ball surface at that point; rotate the tool slightly; measure and mark again. After this process has been repeated a number of times, the series of marks will indicate the desired arc. The drilling technician must then sketch the complete arc. The technician's skill in sketching a smooth arc, and the number of measured marks created on the ball surface will determine the accuracy of the arc. When locating the bowler's positive axis point with regard to only a single ball property indicator only a single arc is needed. When locating a desired positive axis point with reference to 2 of the ball property indicators, 2 arcs must be drawn. The positive axis point will then be located at one of the spots where the 2 arcs cross. Drilling layouts referencing all 3 of the ball property indicators require 3 arcs to be drawn. Although the device in U.S. Pat. No. 5,603,165 to Bernhardt and Laskow (1997) has a provision for drawing an accurate arc, an arc of radius 3⅜ inches is the only size which may be directly drawn. Drawing arcs of radii other than 3⅜ inches on the ball surface is accomplished using the technique described above when employing any of the prior art devices. Obtaining an accurate arc shape of desired radius using prior art tools is very tedious and time consuming.
Once the desired location of the positive axis point has been determined the drilling technician must use the bowler's axis coordinates to determine the location and orientation of the gripping holes in the bowling ball. This process involves drawing the same series of lines as described previously to find the horizontal and vertical axis coordinates for a bowler. Once again this operation consumes a large amount of time. Additional time may be required if the determined location of the gripping holes could cause undesirable results such as drilling too close to the reference pin, or an excessive amount of static imbalance within the ball. In these cases the same positive axis point location is used, but the orientation of the axis coordinate lines are rotated slightly to allow for a different orientation of the gripping holes while still retaining the desired rotational characteristics of the bowling ball.
A second layout technique uses the angle created by a line connecting the reference pin and center of gravity and a line connecting the reference pin and positive axis point, and the distance from the reference pin to the positive axis point as a way of locating the desired positive axis point. Of the prior art tools the device disclosed in U.S. Pat. No. 5,603,165 to Bernhardt and Laskow as this is the only device currently commercially available which has provisions for accurately marking angular measurements on the surface of a bowling ball. The procedure for drawing an angle using this tool is to orient the tool in the desired position to draw the reference pin to center of gravity line; draw this line; orient the tool to measure an angle with the reference pin at the vertex and of the desired offset from the reference pin to center of gravity line; mark the desired angular displacement; re-orient the tool to draw the angled line from the reference pin; measure and mark the desired distance of the positive axis point from the reference pin along the angled line. Once again, this takes more time than should be necessary to accomplish this task.
As in the previous case, once the location of the positive axis point is determined the axis coordinates are used to determine the location and orientation of the gripping holes. Also as in the previous case, if the determined location of the gripping holes is not acceptable then re-measuring from the desired positive axis point at a slightly rotated orientation is required. Much time may be wasted using prior art tools to achieve acceptable layouts with respect to the various physical properties of the bowling ball.